a) Field of the Invention
This invention relates to a process and apparatus for treating a variety of substratesxe2x80x94such as wafers, glass substrates or ceramic substrates for forming semiconductor devices thereon (hereinafter called xe2x80x9csubstratesxe2x80x9d)xe2x80x94by cleaning off, subsequent to formation of a fine arrangement of electrical component parts or a circuit (hereinafter may be commonly called xe2x80x9cpatternxe2x80x9d) on the substrates, foreign matter such as organic matter remaining on the substrates and other foreign matter adhered during or after the formation of the pattern.
The term xe2x80x9cozone waterxe2x80x9d as used herein means water which is available by dissolving an ozone-containing gas in ultrapure water. The term xe2x80x9chydrogen waterxe2x80x9d as used herein means water which is available by dissolving a hydrogen-containing gas in ultrapure water. Further, the term xe2x80x9cozone-hydrogen waterxe2x80x9d as used herein means water which is available by dissolving an ozone-containing gas and a hydrogen-containing gas in ultrapure water or by mixing ozone water and hydrogen water.
b) Description of the Related Art
When forming a pattern on a substrate, an organic material such as a photoresist (hereinafter called a xe2x80x9cresistxe2x80x9d) is coated on the substrate, exposed and then developed to form a desired resist pattern, and the substrate is thereafter subjected to treatment such as etching at a surface thereof. Subsequent to this treatment, any unnecessary resist on the substrate is removed.
After the removal of the resist, it is necessary to clean off very small pieces of the resist, said pieces still remaining on the substrate, and other foreign matter adhered during or subsequent to the formation of the pattern. Conventional cleaning processes for this purpose are classified into wet processes or dry processes depending on the kinds and properties of the resists and the forming steps of component parts.
In the wet processes, a chemical solution which contains sulfuric acid, hydrogen peroxide or the like as a principal component and has oxidizing power is used in many instances (SPM treatment). In the dry processes, on the other hand, organic matter or the like on a substrate is removed by ashing the same while using oxygen as a primary process gas. Depending on the state of contamination of a substrate, cleaning treatment is also performed making appropriately combined use of ashing treatment with oxygen plasma, SPM treatment, and treatment with a chemical solution containing ammonia and hydrogen peroxide or the like as principal components (APM treatment).
As illustrative conventional techniques for such treatment of substrates, JP 10-298589 A discloses a process in which subsequent to plasma ashing of a resist, organic matter and the like on a substrate are removed using ozone water with a basic fluoride added therein. A process is proposed in JP 9-255998 A, in which ultraviolet rays are irradiated in the presence of ozone gas to remove fine organic particles which are remaining on a substrate. JP 10-41262 A discloses to use carbonated water or hydrogen water, which has been prepared by dissolving hydrogen gas in ultrapure water, for the removal of fine metal particles while minimizing corrosion of a pattern such as metalization, i.e., a deposited film pattern of a conductor material. Further, it is proposed in JP 10-128253 A to clean and rinse a substrate under exposure to supersonic waves in hydrogen water which has been prepared by dissolving hydrogen gas to a concentration of 0.05 ppm or higher in ultrapure water.
The cleaning with ozone water subsequent to ashing as disclosed in JP 10-298589 A involves a potential problem in that a substrate may be damaged as the plasma ashing is performed with high energy, and the cleaning treatment with the ozone water is accompanied by a further potential problem in that the damage may be deteriorated. In addition, surface roughening may also occur by a cause other than the plasma ashing, and the cleaning with the ozone water has a potential problem in that damage may be spread from such surface roughening. The process disclosed in JP 9-255998 A, in which ultraviolet rays are irradiated in the presence of ozone, is intended for fine organic particles, and cannot be applied for stripping a resist. The cleaning with ozone water, which is disclosed in JP 10-41262 A, is intended to remove fine metal particles, and the effect of the ozone water depends upon the concentration of ozone contained in the ozone water. The concentration of ozone in conventional ozone water, which is available at room temperature under the surrounding atmospheric pressure, is its saturated concentration at the maximum, and therefore, this cleaning process is not considered to be effective for the removal of organic matter still remaining after dry ashing of a resist. Further, the process disclosed in JP 10-128253 A, in which a substrate is soaked in hydrogen water prepared by dissolving hydrogen gas to a concentration of 0.05 ppm or higher in ultrapure water and is exposed to ultrasonic waves, relates to rinsing treatment, and this patent publication makes no mention about the removal of a residue of a resist after dry ashing of the resist.
Of these conventional processes, the wet processes use one or more chemicals such as sulfuric acid, hydrogen peroxide and/or ammonia upon treatment, and may develop one or more defects in a formed pattern due to formation of sulfuric acid vapor, which gives detrimental effects such as corrosion to a substrate, or due to incorporation of a metal component such as iron due to the use of ammonia. Avoidance of these problems leads to a further problem that subsequent to the treatment, a great deal of cleaning water is needed, resulting in a substantial load of effluent on the environment. On the other hand, the use of oxygen plasma in the dry processes involves a problem in that a substrate, which is chemically sensitive, and a pattern formed on the substrate may be damaged because the plasma has high energy.
An object of the present invention is, therefore, to provide a substrate treatment process and apparatus, which can achieve similar cleaning effects as the conventional techniques without needing use of sulfuric acid, hydrogen peroxide, ammonia, oxygen plasma and/or the like as an essential requirement and without causing production of harmful vapor, incorporation of a metal component such as iron, damage to a substrate, a pollutant load on the environment, or the like.
The above-described object can be achieved by the present invention. In one aspect of the present invention, there is thus provided a substrate treatment process for removing organic matter existing on a substrate, which comprises the following consecutive steps:
treating said substrate with ozone water which has been prepared by dissolving an ozone-containing gas in ultrapure water; and
treating said substrate with hydrogen water which has been prepared by dissolving a hydrogen-containing gas in ultrapure water.
In another aspect of the present invention, there is also provided a substrate treatment process for removing organic matter existing on a substrate, which comprises the following step:
treating said substrate with ozone-hydrogen water, which has been prepared by dissolving an ozone-containing gas and a hydrogen-containing gas in ultrapure water, or with ozone-hydrogen water prepared by mixing ozone water, which was in turn prepared by dissolving an ozone-containing gas in ultrapure water, and hydrogen water which was in turn prepared by dissolving a hydrogen-containing gas in ultrapure water; or treating said substrate with said ozone water and said hydrogen water at the same time.
In a further aspect of the present invention, there is also provided a substrate treatment apparatus for a substrate, comprising:
a treatment vessel,
a substrate holder for rotating said substrate in a horizontal plane in said treatment vessel,
a nozzle unit arranged in an upper part of said treatment vessel such that a liquid is downwardly fed,
a feed line for feeding the liquid to said nozzle unit, and
a chamber enclosing therein said apparatus in its entirety;
wherein said nozzle unit is constructed in a form of a bar such that as viewed in plan, the liquid ejected from said nozzle unit reaches, with an area range having a length not smaller than a diameter of said substrate and a width smaller than said diameter of said substrate, said substrate. The substrate treatment apparatus is suited for practicing the substrate treatment processes.
The processes according to the present invention use only ozone and hydrogen waters or ozone-hydrogen water to remove unnecessary resist after formation of an arrangement of electrical component parts or a circuit, that is, a pattern on a substrate, and therefore, are low-cost processes which give neither substantial pollutant load on the environment nor damage to the pattern. The processes of the present invention are expected to minimize corrosion-related reductions in electrical characteristics of a device and hence to bring about improvements in production yield, so that they make it possible to lower the running cost of a semiconductor fabrication system and also to improve the safety. As is appreciated from the foregoing, the series of treatments in the cleaning step subsequent to the stripping of a resist, said treatments making use of ozone and hydrogen waters or ozone-hydrogen water, can solve various problems in future manufacturing business, such as energy conservation, owing to a reduction in the pollutant load on the environment and simplification of the device forming steps.
Fine particles existing on a substrate, such as pieces of a resist, have heretofore been removed using sulfuric acid, ammonia, hydrogen peroxide, organic solvent or the like. As the processes of the present invention do not use these chemical solutions, they do not significantly corrode the arrangement of component parts or the interconnecting conductive material. Damage to the arrangement of the component parts or the circuits is thus reduced, leading to improvements, for example, in the reliability of performance of the device. This can obviate a step for the prevention of corrosion or, even if such a step is still needed, the cost of materials employed for such treatments can be reduced. On the other hand, the reduction in the corrosion to the interconnecting conductive material leads a reduction in the electrical resistance of the device, a reduction in the power consumption by the device, and a higher speed in the performance of the device.
The conventional treatment in which hydrogen water is used in an activated form is said to permits removal of very fine particles. The processes of the present invention have a significance in that owing to the above-described combination of the treatment with ozone water and the treatment with hydrogen water or the above-described use of ozone-hydrogen water, steps ranging, for example, from the stripping of a resist or the like to the subsequent cleaning can be conducted together without using a conventional chemical solution of high purity such as sulfuric acid. Use of the processes and apparatus according to the present invention, which have enabled it, has made it possible for the first time to perform the treatment.
According to the present invention, the resist stripping step and the cleaning step can be conducted together. This has made it unnecessary to carry each substrate from one processing step to another, thereby brining about merits such as a reduction in the risk to contact a dangerous chemical solution and a reduction in the risk to contact a pollutant. Owing to these merits, the single-step treatment can contribute to a reduction in cost.